1. Field of the Invention
The present invention relates to a cigarette filter.
2. Description of the Related Art
It has been pointed out that active oxygen species and free radicals generally have high reactivity and have relevance to various diseases. It is known to the art that free radicals are contained in cigarette mainstream smoke. Thus, attentions are paid to removal of the free radicals from the cigarette mainstream smoke. It is assumed that the free radicals (alkyl radicals and alkoxy radicals) contained in the vapor phase of the cigarette mainstream smoke excluding the particulate phase component are originated from precursors of nitrogen monoxide and olefins such as isoprene (see Daniel F. Church and William A. Pryor, Environmental Health Perspectives, Vol. 64, pp. 111-126 (1985); and Kaneko et al, Safety Engineering, Vol. 29, pp. 20-26 (1990)). It should be noted that the vapor-phase free radicals cannot be removed with an ordinary fibrous bed filter such as an acetate filter and a paper filter.
Conventionally, it has been attempted to reduce the free radicals by adding various antioxidants to the cigarette filter.
For example, it is known an example of a filter to which a radical scavenger such as benzoquinone and vitamin C is added (see Japanese Patent Application No. 62-232371). However, these radical scavengers are incapable of producing a sufficient effect of reducing the free radicals.
Also, it is known another example of a filter to which an antioxidant derived from soybean ferment is added (see Japanese Patent Application No. 6-62824). However, since measurements are made only for active oxygen species in this document, whether the antioxidant has the effect of reducing the free radicals is unknown.
Further, it is known another example of a filter to which rosemary extract is added (see Japanese Patent Publication (Kohyo) No. 2001-526913). However, since the rosemary extract has an aroma, there is a possibility that it affects taste and flavor of the cigarette.
An object of the present invention is to provide a cigarette filter capable of reducing vapor-phase free radicals without affecting taste and flavor of the cigarette.